Transcript for Kate Upton on why she is accusing Guess Inc. co-founder of sexual harassment

She's one of the most sought after models working today. At 25 years old Kate Upton has risen to the top of the competitive modeling game, bracing the cover of the "Sports illustrated" swim suit issue three times. Starring in commercials. ??? And landing roles in movies like "The other woman". You smell amazing what is that? I think it's just sweat. And the lay over. Forward one and half peck. But seven years ago at just 18 years old it was this campaign for the retailer "Guess" that launched her career. These glamorous images she says hiding a dark reality. Upton is now coming forward claiming the company's founder Paul Marciano sexually assaulted and emotionally abused her while she was shooting the campaign. She shared her story with robin Roberts. I was going back and forth sharing the story because it's always easier to leave things in the past. Upton first alleging the result in time magazine where she said Marciano forcibly grabbed my breast and after I pushed him away he said I'm making sure they're real and he started to kiss my face and neck. Upton claims she was harassed and insulted in subsequent shoots alleging Marciano once called her a fat pig on set. It's a new climate. Women are come together. You're able to have that platform, share your story and create real change for other women and for this industry and for the better. You said it has had a real impact. It did. Made me question what I was doing. How I was putting myself out there to be treat in this way. And you start blaming yourself and you try to change yourself. Slumping my shoulders, wearing baggier clothes and I had to go through this moment where I was like it is not my fault it's his fault, it's his way of acting and I had to empower myself again. Marciano denies her claims calling them preposterous saying he had never been alone with her or touched her inappropriately and fully supports the #metoo movement but will not allow others defame me. I don't need his validation what happened, I'm not looking for him to come forward and tell the truth, honestly I expected him to do that, I think it speak stoz how he treated these allegations in the past. Used to work before and it's not the case any more, we're bpg heard and being taken seriously. A photographer corroborated her account with ABC new I came in with the photographer and he did it right in front of him. After that I had to come up with a lot of different strategies to make sure I wasn't in the same room with him alone. Paul Marciano says he welcomes an investigation and will cooperate fully, would you do the same being involved in an investigation? Yes I think it's really important and honestly I think that it would be so nice to see big corporations and businesses doing this on their own. I think it's really important for employees and everyone to be educated on exactly what sexual harassment is and what consent means so that everyone feels safe inside their professional setting and everyone feels confident in how they're treating each other. In a statement today guess sthed do not condone much misconduct in any form and they have a committee of two independent directors to oversee an ongoing investigation dmoo recent allegations of improp conduct by Marciano. Has guess or anyone from guess contacted you since the article? No, they have not. Would you want to speak with anybody there? I think if it bettered their investigation, yes. But I really have no need to speak to them. So what would you like to see happen next, Kate? Next I would love for people around these people to come out so that they're not enabling them so that victims not only have to live through this and then relive it again when they come out with their story, but they shouldn't be also expected to change the entire culture inside all these corporations and businesses, it should be the people around wanting to make the workplace better and give everybody equal opportunities. What do you say to people who ask you why you didn't say something then when it first happened can you help them understand the difficulty. You know what, because it was a completely different world had it happened, and I was 18 years old, and everybody around me were pushing me to not tell my story,s better to keep things in the dark, or just go. Because everyone is incentivized by me getting on set. The agent. Everybody gets paid if I show up on set. So you are constantly pushed to show up on set no matter what happens and they bring up other examples of other who's are fine with this behavior and have really successful careers. You are also having doubt in my mind, how I acted, did I ask for this treatment, but you didn't. This is their behavior I think the wait a minute who came out before and after me really proved that. Kate Upton saying me too hoping her story will change a culture and other women. For "Nightline" Lindsey Janice in New York. Our thanks to robin and Lindsey.

This transcript has been automatically generated and may not be 100% accurate.

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